Embodiments relate to a light emitting device, a light emitting device package, and a lighting system.
In light emitting devices, P-N junction diodes having the properties of converting electrical energy into light energy may be formed by combining group III and V elements on the periodic table. Light emitting devices may implement various colors by controlling the composition ratio of compound semiconductors.
In light emitting devices, when a forward voltage is applied, an electron of an n-layer is combined with a hole of a p-layer to emit energy corresponding to an energy gap between the conduction band and the valance band. The energy is generally emitted in the form of heat or light. In light emitting devices, the energy is emitted in the form of light.
Nitride semiconductors, for example, are attracting much attention for the fields of optical devices and high-power electronic devices because of their high thermal stability and wide band gap energy. In particular, blue light emitting devices, green light emitting devices, and UV light emitting devices that use nitride semiconductors have been commercialized and are widely used.
A white LED module in the related art may be formed by combining separate light sources of R, G, and B or by combining a phosphor and a blue or ultra violet light source.
In a typical phosphor conversion method using a yellow phosphor applied to the outside of a blue LED, light converted at the phosphor is naturally emitted, and thus, the light is emitted forward. At this point, light may be incident again into a light emitting device and be absorbed in the device to cause an optical loss and degrade light emitting efficiency.